Add lots and lots of missing operations
Add lots and lots of missing operations

- Scalar multiplication of vectors and matrices
  - This was present for only vec2's and vec3's using operator
    overloading. In addition, there was only operator overloading for
    [structure] * float, not float * [structure].
  - Additionally, the two operators that were already defined were
    updated to use the new C-style functions that were defined.
- Scalar division of vectors and matrices
- Matrix subtraction
- += operator for matrices

HandmadeMath/Handmade-Math,HandmadeMath/Handmade-Math